Spiralling into Dark Energy: Axio-Dilaton Attractors in Light of Current Data
Abstract
In string compactifications, dilaton-like moduli always come paired with axions, and the two fields interact through a curved field-space metric. We study the cosmology of such an axio-dilaton system, in which the dilaton rolls down an exponential potential corrected by a polynomial prefactor and couples to a massless axion through the kinetic function W=e−ξϕ1/Mp. A dynamical systems analysis shows that the late-time attractor follows a non-geodesic trajectory in field space with equation of state ωϕ=(λ−2ξ)/(λ+2ξ), so accelerated expansion is possible for steep potentials provided ξ≫λ. No physical fixed point is phantom. A Bayesian analysis with DESI DR2 BAO, binned Pantheon supernovae and Planck 2018 distance priors gives λ≳7--$9$ and log10ξ≳2.5 at 95% confidence, together with a degeneracy between the two parameters. The model is slightly favoured over ΛCDM by current data, while the different polynomial corrections cannot yet be distinguished. This contribution is based on arXiv:2609.22539.
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BibTeX
@misc{ramoshamud2026spiralling,
title = {{Spiralling into Dark Energy: Axio-Dilaton Attractors in Light of Current Data}},
author = {Mario Ramos-Hamud},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34380},
eprint = {2610.34380},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34380},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Spiralling into Dark Energy: Axio-Dilaton Attractors in Light of Current Data
AU - Mario Ramos-Hamud
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2610.34380
UR - https://arxiv.org/abs/2610.34380
AB - In string compactifications, dilaton-like moduli always come paired with axions, and the two fields interact through a curved field-space metric. We study the cosmology of such an axio-dilaton system, in which the dilaton rolls down an exponential potential corrected by a polynomial prefactor and couples to a massless axion through the kinetic function W=e^−ξϕ_1/M_p. A dynamical systems analysis shows that the late-time attractor follows a non-geodesic trajectory in field space with equation of state ω_ϕ=(λ−2ξ)/(λ+2ξ), so accelerated expansion is possible for steep potentials provided ξ≫λ. No physical fixed point is phantom. A Bayesian analysis with DESI DR2 BAO, binned Pantheon supernovae and Planck 2018 distance priors gives λ≳7--$9$ and log_10ξ≳2.5 at 95% confidence, together with a degeneracy between the two parameters. The model is slightly favoured over ΛCDM by current data, while the different polynomial corrections cannot yet be distinguished. This contribution is based on arXiv:2609.22539.
ER -